1. Field of the Invention
This invention relates to compressors and more particularly to the maintenance of a pressurized oil supply during compressor operation without the need for a mechanical pump.
2. Description of the Related Art
A typical refrigeration system using a helical compressor and an oil pump for circulation is disclosed in the Short U.S. Pat. No. 4,916,914. The Bixler U.S. Pat. No. 2,338,486 also discloses oil circulation by a pump. In Bixler the compressor is kept unloaded until the oil pressure provided by the lubricating pump is adequate.
The Shoemaker U.S. Pat. No. 2,418,853 discloses a compressor system having a valve in a suction line which shuts down if the pressure is below a predetermined minimum, thereby maintaining a predetermined pressure in the compressor crank case.
The Kagi U.S. Pat. No. 2,155,051 discloses a gravity operated check valve in a compressor discharge which leads to an oil separator whereby oil is separated as required. The Williams U.S. Pat. No. 2,128,388 discloses a system in which during compressor operation oil under pressure opens a valve to permit oil from the crank case to flow to a reservoir.
The Kish U.S. Pat. No. 3,827,255 discloses a conventional spring biased check valve in the discharge line from a compressor.
The Huenniger U.S. Pat. No. 4,653,286 and 4,749,166 disclose a discharge valve and baffle assembly connected to the condenser of a centrifugal compressor discharge and operative to remain closed until the compressor reaches operating speed, dependent upon the compressor operating suction pressure.